Inventory - why is the "Standard Cost" field GST inclusive when nothing else is?

As the title states.

It is insanely irritating that I have to manually add GST to every single item I enter into my Accountright inventory in the "Buying Details" field.

If the price given by my supplier is $20 excl GST I can't enter that. I have to enter $22 or else when I go to create a Purchase Order it will reduce it.

Yet when I enter the SELL price in the "Selling Details" tab I don't have to enter the **bleep**ing price inclusive of GST. 

Why is this product so backwards?